Chikungunya

Chikungunya is a relatively rare form of viral fever caused by an alphavirus that is spread by mosquito bites.

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Etymology

The name is derived from the Makonde word meaning "that which bends up" in reference to the stooped posture developed as a result of the arthritic symptoms of the disease. The disease was first described by Marion Robinson^[1] and W.H.R. Lumsden^[2] in 1955, following an outbreak on the Makonde Plateau, along the border between Tanganyika and Mozambique, in 1952.

Linguistic confusion

According to the initial 1955 report about the epidemiology of the disease, the term chikungunya is derived from the Makonde root verb kungunyala, meaning to dry up or become contorted. In concurrent research, Robinson glossed the Makonde term more specifically as "that which bends up." Subsequent authors apparently overlooked the references to the Makonde language and assumed that the term derived from Swahili, the lingua franca of the region. The erroneous attribution of the term as a Swahili word has been repeated in numerous print sources. Many other erroneous spellings and forms of the term are in common use including "Chicken guinea", "Chicken gunaya," and "Chickengunya".^{[citation needed]}

Epidemiology

Chikungunya virus is an alphavirus closely related to the O'nyong'nyong virus,^[3] the Ross River virus in Australia, and the viruses that cause eastern equine encephalitis and western equine encephalitis.^[4]

  Chikungunya is generally spread through bites from Aedes aegypti mosquitoes, but recent research by the Pasteur Institute in Paris suggested that chikungunya virus strains from the 2005-2006 Reunion Island outbreak incurred a mutation that facilitated transmisson by Aedes albopictus (Tiger mosquito).^[5] Concurrent studies by arbovirologists at the University of Texas Medical Branch in Galveston Texas confirmed definitively that enhanced chikungunya virus infection of Aedes albopictus was caused by a point mutation in one of the viral envelope genes (E1). ^[6][7]. Enhanced transmission of chikungunya virus by Aedes albopictus could mean an increased risk for chikungunya outbreaks in other areas where the Asian tiger mosquito is present. A recent epidemic in Italy was likely perpetuated by Aedes albopictus.^[8]

In Africa, chikungunya is spread via a sylvatic cycle in which the virus largely resides in other primates in between human outbreaks.^[4]

Outbreaks

Main article: Chikungunya outbreaks

Since its discovery in Tanzania, Africa in 1952, chikungunya virus outbreaks have occurred occasionally in Africa, South Asia, and Southeast Asia, but recent outbreaks have spread the disease over a wider range.

• The first outbreak in India was in 1963 in Kolkata (Calcutta).^[9]
• An outbreak of chikungunya was also discovered in Port Klang in Malaysia in 1999 affecting 27 people [2][3].
• There was an outbreak in Italy late 2007, with 160 cases.^[10]
  • At the same time there was an outbreak in Kerala with 43,138 cases of suspected chikungunya.^[11]
• 2005-2006, 237 deaths were associated with chikungunya on Réunion island and one third of the island's population were infected.^[12] There was also a widespread outbreak in India, primarily in Tamil Nadu, Karnataka, Kerala, and Andhra Pradesh.
• After flood and heavy rains in Rajasthan, India in August 2006, thousands of cases were detected in Rajsamand, Bhilwara, Udaipur, and Chittorgarh districts and also in adjoining regions of Gujarat and Madhya Pradesh, and in the neighbouring country of Sri Lanka.
• In the southern Indian state of Kerala, 125 deaths were attributed to Chikungunya with the majority of the casualties reported in the district of Alapuzha, primarily in Cherthala.
• In December 2006, an outbreak of 3,500 confirmed cases occurred in Maldives, and over 60,000 cases in Sri Lanka, with over 80 deaths.[4]
• In October 2006 more than a dozen cases of chikungunya were reported in Pakistan.
• During June 2007 in Pathanamthitta, Kottayam and Alappuzha districts of South Kerala, India claimed more than 50 lives, though no mortality has definitively been linked to chikungunya virus. It is confirmed officially that there are 7000 confirmed Chikungunya patients in these areas. Unofficial reports suggest that more than one hundred thousand are suffering from symptoms of chikungunya.^{[citation needed]}
• The European Network for Diagnostics of "Imported" Viral Diseases [5] claims that new phylogenetic variants of the virus have been identified on Réunion.[6]
• In August/September 2007, at least 200 people were infected in Italy's northern Ravenna region, resulting in one death.^[13]

Symptoms

The symptoms of Chikungunya include fever which can reach 39°C, (102.2°F) a petechial or maculopapular rash usually involving the limbs and trunk, and arthralgia or arthritis affecting multiple joints which can be debilitating. The symptoms could also include headache, conjunctival injection, and slight photophobia. High fevers and joint pain are found in the current epidemic in the states of Andhra Pradesh and Tamil Nadu, India. The fever typically lasts for two days and then comes down abruptly. However, other symptoms, namely joint pain, intense headache, insomnia and an extreme degree of prostration last for a variable period; usually for about 5 to 7 days. Patients have complained of joint pains for much longer time periods depending on their age. Younger patients recover within 5 to 15 days; middle-agers recover in 1 to 2.5 months. Recovery is longer for the elderly. The severity of the disease as well as its duration is less in younger patients and pregnant women. No untoward effects of pregnancy are noticed following the infection.

Ocular inflammation from Chikungunya may present as iridocyclitis, and have retinal lesions as well.^[14]

Dermatological manifestations observed in a recent outbreak of Chikungunya fever in Southern India (Dr. Arun Inamadar, Dr. Aparna Palit, Dr.V.V. Sampagavi, Dr. Raghunath S, Dr. N.S. Deshmukh), Western India (Surat) (Western India reported by Dr. Buddhadev) and Eastern India (Puri) (Dr. Milon Mitra et al) includes the following:

• Maculopapular rash
• Nasal blotchy erythema
• Freckle-like pigmentation over centro-facial area
• Flagellate pigmentation on face and extremities
• Lichenoid eruption and hyperpigmentation in photodistributed areas
• Multiple aphthous-like ulcers over scrotum, crural areas and axilla.
• Lympoedema in acral distribution (bilateral/unilateral)
• Multiple ecchymotic spots (Children)
• Vesiculobullous lesions (infants)
• Subungual hemorrhage
• Photo Urticaria
• Acral Urticaria
• Cephalgia
• Lumbago
• Vomiting
• Epistaxis and haemetemesis

Histopathologically, pigmentary changes, maculopapular rash, lichenoid rash, aphthous-like ulcers show lymphocytic infiltration around dermal blood vessels (Inamadar et al). Pedal oedema (swelling of legs) is observed in many patients, the cause of which remains obscure as it is not related to any cardiovascular, renal or hepatic abnormalities.

Treatment

There are no specific treatments for Chikungunya. There is no vaccine currently available. A Phase II vaccine trial, sponsored by the US Government and published in the American Journal of Tropical Medicine and Hygiene in 2000, used a live, attenuated virus, developing viral resistance in 98% of those tested after 28 days and 85% still showed resistance after one year.^[15]

A serological test for Chikungunya is available from the University of Malaya in Kuala Lumpur, Malaysia.

Chloroquine is gaining ground as a possible treatment for the symptoms associated with chikungunya and as an antiviral agent to combat the Chikungunya virus. A University of Malaya study found that for arthritis-like symptoms that are not relieved by aspirin and non-steroidal anti-inflammatory drugs (NSAID), chloroquine phosphate (250 mg/day) has given promising results. [7] Research by an Italian scientist, Andrea Savarino, and his colleagues together with a French government press release in March 2006^[16] have added more credence to the claim that chloroquine might be effective in treating chikungunya. Unpublished studies in cell culture and monkeys show no effect of chloroquine treatment on reduction of chikungunya disease. The fact sheet on Chikungunya advises against using aspirin, Ibuprofen, naproxen and other NSAIDs are recommended for arthritic pain and fever.

Infected persons should limit further exposure to mosquito bites, stay indoors and under a mosquito net. Further, "supportive care with rest is preferred during the acute joint symptoms. Movement and mild exercise tend to improve stiffness and morning arthralgia, but heavy exercise may exacerbate rheumatic symptoms."[8] Arthralgia remains troublesome even after 8 months. In Kerala, patients use honey and lime mix. Some people cite relief from consuming turmeric in low volumes.

Preventive measures

The most effective means of prevention are those that protect against any contact with the disease-carrying mosquitos. These include using insect repellents with substances like DEET (also called NNDB or N,N'-Diethyl-3-methylbenzamide), icaridin (also known as picaridin and KBR3023), PMD (p-menthane-3,8-diol, a substance derived from the lemon eucalyptus tree), or IR3535. Wearing bite-proof long sleeves and trousers (pants) also offers protection. In addition, garments can be treated with with pyrethroids, a class of insecticides that often has repellent properties. Vaporized pyrethroids (for example in mosquito coils) also have a certain spacial repellency. Securing screens on windows and doors will help to keep mosquitoes out of the house. In the case of the day active Aedes aegypti and Aedes albopictus, however, this will only have a limited effect, since many contacts between the vector and the host occur outside. Thus, mosquito control is especially important.

See also

• Dengue fever

References